Mos Devices with Ultra-High Dielectric Constants and Methods of Forming The Same

ABSTRACT

An integrated circuit structure includes a semiconductor substrate, and a gate stack over the semiconductor substrate. The gate stack includes a high-k gate dielectric over the semiconductor substrate, and a magnetic compound over and in contact with the high-k gate dielectric. A source region and a drain region are on opposite sides of the gate stack. The gate stack, the source region, and the drain region are portions of a Metal-Oxide-Semiconductor (MOS) device.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. patent application Ser. No.14/245,785, entitled “Mos Devices with Ultra-High Dielectric Constantsand Methods of Forming The Same,” filed on Apr. 4, 2014, whichapplication is incorporated herein by reference.

BACKGROUND

Metal Oxide-Semiconductor (MOS) devices are key components of integratedcircuits. A MOS device includes a gate stack, which further includes agate dielectric over a semiconductor substrate, and a gate electrodeover the gate dielectric. A source region and a drain region aredisposed on the opposite sides of the gate stack. The MOS device may beturned on and off by controlling the voltage applied on the gateelectrode, so that the source region and the drain region are eitherelectrically disconnected or electrically interconnected.

Conventionally, silicon dioxide was used to form the gate dielectrics.With the evolving of integrated circuits, dielectric materials with highdielectric constants (high-k values) are increasingly used to form thegate dielectrics. The high-k dielectrics may improve the short channelcontrol of the MOS devices. The high-k dielectrics may also reduce gateleakage currents. Hafnium oxide and aluminum oxide are among knownhigh-k dielectric materials.

It is desirable to have high-k materials with the k values higher thanthe currently used high-k dielectric materials in order to furtherimprove the performance of the MOS devices. However, higher k valuesalso result in problems. For example, with the further increase in the kvalues, the band-gaps of the high-k dielectric materials reduce, whichresults in the gate leakage currents of the respective MOS devices to beincreased. Therefore, tradeoff has to be made to choose between higher kvalues accompanied by higher leakage currents and lower k-valuesaccompanied by lower leakage currents.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 12 illustrate the cross-sectional views of intermediatestages in the formation of a Metal-Oxide-Semiconductor (MOS) device inaccordance with some exemplary embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “underlying,” “below,”“lower,” “overlying,” “upper” and the like, may be used herein for easeof description to describe one element or feature's relationship toanother element(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

A Metal-Oxide-Semiconductor (MOS) device and the method of forming thesame are provided in accordance with various exemplary embodiments. Theintermediate stages of forming the MOS device are illustrated. Thevariations of the embodiments are discussed. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements. In the illustrated embodiments, a gate-lastapproach is used to form the replacement gate stack of the MOS device.It is appreciated that teaching regarding the materials and theformation methods of the gate stack is readily applicable to forming aMOS device using a gate-first approach, in which the gate stack isformed before the formation of source and drain regions of the MOSdevice.

FIGS. 1 through 12 are cross-sectional views of intermediate stages inthe formation of a MOS device in accordance with some exemplaryembodiments. Referring to FIG. 1, wafer 10, which includes substrate 20,is provided. Substrate 20 may be formed of a semiconductor material suchas silicon, silicon carbon (SiC), silicon germanium (SiGe), a III-Vcompound semiconductor, or the like. Isolation regions such as ShallowTrench Isolation (STI) regions 21 are formed in substrate 20, and areused to define the active regions of MOS devices.

Dummy gate stack 22 is formed over substrate 20. Dummy gate stack 22includes dummy gate dielectric 24 and dummy gate electrode 26. Dummygate dielectric 24 includes silicon oxide in some exemplary embodiments.In alternative embodiments, other materials such as silicon nitride,silicon carbide, or the like, are also used. Dummy gate electrode 26 mayinclude polysilicon. In some embodiments, dummy gate stacks 22 furtherincludes hard mask 28 over dummy gate electrode 26. Hard mask 28 maycomprise silicon nitride, for example, while other materials such assilicon carbide, silicon oxynitride, and the like may also be used. Inalternative embodiments, hard mask 28 is not formed.

Lightly-Doped Drain/source (LDD) regions 30 are formed, for example, byimplanting a p-type impurity (such as boron and/or indium) or an n-typeimpurity (such as phosphorous and/or arsenic) into substrate 20,depending on the conductivity type of the resulting MOS device 100 (FIG.10). For example, when MOS device 100 is a pMOS device, LDD regions 30are p-type regions. When the MOS device 100 is an nMOS device, LDDregions 30 are n-type regions. Dummy gate stacks 22 acts as animplantation mask, so that the edges of LDD regions 30 are substantiallyaligned with the edges of gate stacks 22.

Referring to FIG. 2, gate spacers 34 are formed on the sidewalls ofdummy gate stack 22. In some embodiments, each of gate spacers 34includes silicon oxynitride layer 34A and silicon oxide layer 34B. Inalternative embodiments, gate spacers 34 include one or more layers,each comprising silicon oxide, silicon nitride, silicon oxynitride, orother dielectric materials. The available formation methods includePlasma Enhanced Chemical Vapor Deposition (PECVD), Low-Pressure ChemicalVapor Deposition (LPCVD), Sub-Atmospheric Chemical Vapor Deposition(SACVD), and other deposition methods.

Source and drain regions (referred to as source/drain regionshereinafter) 38 are formed in semiconductor substrate 20. In theembodiments wherein MOS device 100 (FIG. 10) is a pMOS device,source/drain regions 38 are of p-type. In the embodiments wherein MOSdevice 100 is an nMOS device, source/drain regions 38 are of n-type. Insome embodiments, source/drain stressors (also marked as 38) are formedin semiconductor substrate 20. The source/drain stressors form at leastparts of source and drain regions 38. FIG. 2 illustrates the embodimentsin which source/drain regions 38 fully overlap the respectivesource/drain stressors. In alternative embodiments, source/drain regions38 and the source/drain stressors are partially overlapped.

Furthermore, in the embodiments in which MOS device 100 (FIG. 10) is annMOS device, source/drain stressors 38 may comprise silicon phosphorous(SiP), silicon carbon (SiC), or the like. In the embodiments in whichMOS device 100 is a pMOS device, source/drain stressors 38 may comprisesilicon germanium (SiGe). The formation of source/drain stressors 38 maybe achieved by etching semiconductor substrate 20 to form recessestherein, and then performing an epitaxy to grow source/drain stressors38 in the recesses.

Referring to FIG. 3, Contact Etch Stop Layer (CESL) 40 is formed overgate stack 22 and source/drain regions 38. In some embodiments, CESL 40comprises silicon nitride, silicon carbide, or other dielectricmaterials. Inter-Layer Dielectric (ILD) 42 is form over CESL 40. ILD 42is blanket formed to a height higher than the top surface of dummy gatestack 22. ILD 42 may comprise Flowable oxide formed using, for example,Flowable Chemical Vapor Deposition (FCVD). ILD 42 may also be a spin-onglass formed using spin-on coating. For example, ILD 42 may comprisePhospho-Silicate Glass (PSG), Boro-Silicate Glass (BSG), Boron-DopedPhospho-Silicate Glass (BPSG), Tetraethyl Orthosilicate (TEOS) oxide,TiN, SiOC, or other low-k non-porous dielectric materials.

FIG. 4 illustrates a planarization step, which is performed using, forexample, Chemical Mechanical Polish (CMP). The CMP is performed toremove excess portions of ILD 42 and CESL 40, wherein the excessportions are over the top surface of hard mask 28. Accordingly, dummygate stack 22 is exposed. In alternative embodiments, hard mask 28 isremoved during the CMP, wherein the CMP stops on the top surface ofdummy gate electrode 26.

Next, dummy gate stack 22 is removed. Recess 44 is formed as a result ofthe removal of dummy gate stack 22, wherein the resulting structure isshown in FIG. 5. In some embodiment, the width W1 of recess 44 issmaller than about 25 nm, and may be in the range between about 18 nmand about 22 nm. It is appreciated, however, that the values recitedthroughout the description are merely examples, and may be changed todifferent values. Furthermore, depth D1 of recess 44 may be greater thanabout 10 nm. The aspect ratio D1/W1 of recess 44 may be higher thanabout 5, higher than about 7, or higher than about 10. Such high aspectratio, small width W1, and great depth D1 demand the subsequently formedmetal layers to be conformal in order to achieve the requiredperformance.

FIGS. 6 through 11 illustrate the formation of a replacement gate stack.Referring to FIG. 6, gate dielectric layer 46 is formed. In someembodiments, gate dielectric layer 46 may have a k value greater than3.9, and hence is a high-k dielectric layer. The k value of high-k gatedielectric layer 46 may further be higher than about 20. In alternativeembodiments, gate dielectric layer 46 may be a low-k dielectric layerhaving a k value lower than 3.9. In these embodiments, however, the kvalue of gate dielectric layer 46 will be propelled to be high-k by theoverlying magnetic layer as shown in FIG. 7. In some embodiments, beforethe formation of high-k gate dielectric layer 46, an Interfacial Layer(IL, not shown) may be formed at the top surface of semiconductorsubstrate 20, wherein the IL layer is in recess 44. The IL layer mayinclude an oxide layer such as a silicon oxide layer, which may beformed through the thermal oxidation of substrate 20, a chemicaloxidation, or a deposition step.

In some embodiments, gate dielectric layer 46 is formed of a high-kdielectric material, which is formed of BaTiO₃, CoFe₂O₄, YFeO₃, CdCr₂S₄,TbMnO₃, BiFeO₃, or the like. In yet alternative embodiments, gatedielectric layer 46 is formed of HfO₂, Al₂O₃, or the like. In yetalternative embodiments, gate dielectric layer 46 is formed of a low-kdielectric material such as HgCr₂S₄, which has a k value lower than 1(such as about 0.54). The thickness T1 of gate dielectric layer 46 ispreferably small, for example, smaller than about 10 Å. In someembodiments, thickness T1 is in the range between about 5 Åand about 10Å. The formation of gate dielectric layer 46 may be performed using, forexample, Atomic Layer Deposition (ALD). Other methods may also be used.Gate dielectric layer 46 may have a high k value. For example, BaTiO₃may have a k value equal to about 300.

As also shown in FIG. 6, magnetic layer 48 is formed over, and may ormay not be in contact with, gate dielectric layer 46. Magnetic layer 48may be formed of a magnetic compound, which generates magnetic field 49.Magnetic layer 48 may be electrically conductive. In some embodiments,magnetic material 48 comprises iron (Fe) and platinum (Pt). Theformation process and the composition of magnetic material 48 areadjusted to increase the magnetic field generated by magnetic material48. FIG. 6 schematically illustrates the magnetic fields (represented byarrows 49) that are generated by magnetic layer 48. Magnetic fields 49have directions perpendicular to the major surface planes of magneticlayer 48. For example, the bottom portion of magnetic layer 48, with thebottom portion extending horizontally, generates a magnetic field 49penetrating through the underlying horizontal portion of gate dielectriclayer 46, wherein the respective magnetic field 49 is in the verticaldirection. The respective magnetic field 49 is also perpendicular to amajor top surface 20A (FIG. 1) or bottom surface of substrate 20.

On the other hand, the sidewall portions of magnetic layer 48, whichextend vertically, generate magnetic fields 49 penetrating through therespective contacting portions of gate dielectric layer 46, wherein therespective portions of magnetic fields 49 are in the horizontaldirections in FIG. 6. In the embodiments in which BaTiO₃ is used, themagnetic field 49 may have directions as illustrated. In alternativeembodiments in which different magnetic materials are used, the magneticfield 49 may have directions opposite to the illustrated directions.

In some embodiments, magnetic layer 48 has a thickness T2 in the rangebetween about 10 nm and about 500 nm. Thickness T2 may also be in therange between about 100 nm and about 300 nm. The formation of magneticlayer 48 may be performed using, for example, sputtering (Physical VaporDeposition (PVD)). The formation conditions affect the magnitude of themagnetic field 49, and without the proper formation conditions, magneticfield may not be generated. In some embodiments, to induce and increasemagnetic field 49, the chamber for forming magnetic layer 48 may have apressure lower than about 10⁻⁷ torr. The formation temperature is higherthan about 500° C. After the formation, a post-anneal is performed onwafer 10, with the temperature being higher than about 1,000° C. Theoptimum conditions for inducing and increasing magnetic field 49 areaffected by various factors, and may be found through experiments.

In some embodiments, magnetic layer 48 is formed of (or comprises) FePt.An exemplary atomic percentage of Pt in FePt is in the range betweenabout 20 percent and about 80 percent, and the atomic percentage of Fein FePt is in the range between about 80 percent and about 20 percentaccordingly. Experiment results indicated that when the atomic percentof Fe and the atomic percent of Pt are close to each other, the magneticfield 49 generated by magnetic layer 48 is high. In some exemplaryembodiments, an atomic percentage of Pt in FePt is in the range betweenabout 40 percent and about 60 percent, and the atomic percentage of Fein FePt is in the range between about 60 percent and about 40 percentaccordingly. In alternative embodiments, magnetic layer 48 comprisesNiFe, wherein the atomic percentage of Fe in NiFe is in the rangebetween about 20 percent and about 80 percent, and the atomic percentageof Ni in NiFe is in the range between about 80 percent and about 20percent accordingly.

By adjusting the formation process conditions and the composition ofmagnetic layer 48 in combination, magnetic field 49 may be higher thanabout 0.1 Tesla, which is applied on gate dielectric layer 46. Thedipoles in gate dielectric layer 46 are affected by magnetic field 49,and are more oriented in the direction parallel to (or anti-parallel to)the direction of magnetic field 49 than if no magnetic field 49 isapplied. The dipoles may be induced when the respective MOS device isapplied with voltages. This results in the capacitance that is caused bygate dielectric layer 46 to be increased. This is equivalent to that theeffective k value of gate dielectric layer 46 is increased. In someembodiments, depending on the materials of gate dielectric layer 46 andmagnetic layer 48, and the formation processes, the effective k value ofgate dielectric layer 46 may be increased by between about 10 percentand about 10,000 percent (100 times). For example, when gate dielectriclayer 46 is formed of BaTiO₃, and magnetic layer 48 is formed of FePt,the effective k-value of gate dielectric layer 46 may be increased byabout 3 times, and the effective k value of gate dielectric layer 46 maybe about 1,250 to about 10,000. On the other hand, when gate dielectriclayer 46 is formed of HgCr₂S₄, and magnetic layer 48 is formed of FePt,the effective k-value of gate dielectric layer 46 may be increased byabout 120 times, and the effective k-value may be about 65.

Next, as shown in FIG. 7, diffusion barrier layer 50 is formed overmagnetic layer 48. In some embodiments, diffusion barrier layer 50includes TiN, TaN, or composite layers thereof. For example, diffusionbarrier layer 50 may include a TiN layer (the lower part of diffusionbarrier layer 50), and a TaN layer (the upper part of diffusion barrierlayer 50) over the TiN layer.

Referring to FIG. 8, metal layer 52 is formed. In the embodiments inwhich the resulting MOS device 100 (FIG. 12) is an N-type MOS (NMOS)device, metal layer 52 is in contact with diffusion barrier layer 50.For example, in the embodiments in which diffusion barrier layer 50comprises a TiN layer and a TaN layer, metal layer 52 may be in physicalcontact with the TaN layer. Metal layer 52 provides the work functionsuitable for NMOS devices, which work function is lower than the mid-gapwork function. The work function lower than the mid-gap work function isreferred to as an n-work function, and the respective metal having then-work function is referred to as an n-metal. In some embodiments, metallayer 52 is an n-metal having a work function lower than about 4.4 eV.The work function of metal layer 52 may also be in the range betweenabout 4.1 eV and about 4.4 eV. Metal layer 52 may comprise titaniumaluminum (TiAl) (which may include, or free from or substantially freefrom other elements) in accordance with some embodiments. The formationof metal layer 52 may be achieved through Physical Vapor Deposition(PVD).

In alternative embodiments in which the resulting MOS device 100 (FIG.12) is a P-type MOS (PMOS) device, an additional TiN layer (not shown)is formed between, and in contact with, the TaN layer (in diffusionbarrier layer 50) and the overlaying metal layer 52. The additional TiNlayer provides the work function suitable for PMOS devices, which workfunction is higher than the mid-gap work function (about 4.5 eV) that isin the middle of the valance band and the conduction band of silicon.The work function higher than the mid-gap work function is referred toas a p-work function, and the respective metal having the p-workfunction is referred to as a p-metal.

Next, as shown in FIG. 9, layer(s) 54 are formed. In some embodiments,layers 54 include a block layer, which may comprise TiN in someembodiments. Block layer 52 may be formed using Chemical VaporDeposition (CVD). Layers 54 may also include a wetting layer, which hasa good ability to adhere (and wet) the subsequently formed filling metal56 (FIG. 12) during the reflow of filling metal 56. In some embodiments,the wetting layer is a cobalt layer, which may be formed using CVD.

FIG. 10 illustrates the formation of filling metal 56 to fill theremaining portions of recess 44 (FIG. 9). Filling metal 56 may comprisealuminum or an aluminum alloy, which may also be formed using PVD, CVD,or the like. Filling metal 56 may be reflowed to fully fill theremaining recess 44 as in FIG. 9. The formation of wetting layer 54improves the wetting of filling metal 56 to the underlying layers.

FIG. 11 illustrates a planarization step (for example, a CMP) forremoving excess portions of layers 46, 48, 50, 52, 54, and 56, whereinthe excess portions are over ILD 42. The remaining portions of layers46, 48, 50, 52, 54, and 56 form replacement gate stack 58. Each of theremaining portions of layers 46, 48, 50, 52, 54, and 56 may include abottom portion, and sidewall portions over and connected to the bottomportion.

Referring to FIG. 12, source/drain silicide regions 60 and contact plugs62 are formed. The formation process may include forming contact plugopenings in ILD 42 to expose source/drain regions 38, forming a metallayer (not shown) to extend into the contact plug openings, performingan annealing to form the source/drain silicide regions 60, removing theun-reacted portions of the metal layer, and filling the contact plugopenings to form contact plugs 62. MOS device 100 is thus formed.

When the gate-first approach is used, the structure of MOS device 100 issimilar to what is shown in FIG. 12, except that that the layers, suchas 46, 48, 50, 52, 54, and 56, in gate stack 58 are horizontal withoutincluding the vertical portions. One of ordinary skill in the art willrealize the formation details of the respective MOS device by applyingthe teaching of the present disclosure.

The embodiments of the present disclosure have some advantageousfeatures. By forming a magnetic layer over the high-k dielectric layer,the effective k value of the high-k dielectric layer, affected by themagnetic field, is increased. On the other hand, the increase in the kvalue of the high-k dielectric layer does not result in the reduction inthe bandgap of the high-k dielectric layer. Accordingly, the gateleakage current is not increased.

In accordance with some embodiments of the present disclosure, a MOSdevice includes a semiconductor substrate, a gate dielectric over thesemiconductor substrate, and a magnetic layer over the gate dielectric.

In accordance with alternative embodiments of the present disclosure, anintegrated circuit structure includes a semiconductor substrate, and agate stack over the semiconductor substrate. The gate stack includes ahigh-k gate dielectric over the semiconductor substrate, and a magneticcompound over and in contact with the high-k gate dielectric. A sourceregion and a drain region are on opposite sides of the gate stack. Thegate stack, the source region, and the drain region are portions of aMOS device.

In accordance with yet alternative embodiments of the presentdisclosure, a method includes forming a gate stack over a semiconductorsubstrate. The formation of the gate stack includes forming a high-kgate dielectric over the semiconductor substrate, and forming a magneticcompound over the high-k gate dielectric. A source region and a drainregion are formed on opposite sides of the gate stack, wherein the gatestack, the source region, and the drain region are portions of a MOSdevice.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a gate stack over asemiconductor substrate, wherein the forming the gate stack comprises:forming a high-k gate dielectric over the semiconductor substrate; anddepositing a magnetic compound over the high-k gate dielectric 46; andforming a source region and a drain region on opposite sides of the gatestack, wherein the gate stack, the source region, and the drain regionare portions of a Metal-Oxide-Semiconductor (MOS) device.
 2. The methodof claim 1, wherein the high-k gate dielectric is in contact with themagnetic compound, and wherein a magnetic field generated by themagnetic compound penetrates through, and is perpendicular to, a majorsurface plane of the high-k gate dielectric.
 3. The method of claim 2,wherein the magnetic field is in a direction point from the magneticcompound to the high-k gate dielectric.
 4. The method of claim 2,wherein the magnetic field is in a direction point from the high-k gatedielectric to the magnetic compound.
 5. The method of claim 1, whereinthe forming the magnetic compound comprises: depositing the magneticcompound using sputtering, wherein the sputtering is performed at atemperature higher than about 500° C.; and after the sputtering,performing an annealing on the magnetic compound at a temperature higherthan about 1,000° C.
 6. The method of claim 1, wherein the forming thehigh-k gate dielectric comprises forming a layer comprising BaTiO₃,CoFe₂O₄, YFeO₃, CdCr₂S₄, HgCr₂S₄, TbMnO₃, or BiFeO₃.
 7. The method ofclaim 1, wherein the depositing the magnetic compound comprisesdepositing a FePt layer.
 8. The method of claim 1, wherein the formingthe magnetic compound comprises depositing a NiFe layer.
 9. A methodcomprising: removing a dummy gate between gate spacers to form anopening; forming a gate dielectric extending into the opening;depositing a magnetic layer over the gate dielectric and extending intothe opening; depositing a work function layer over the magnetic layer;filling a remaining portion of the opening with a metallic material;performing a planarization to remove excess portions of the gatedielectric, the magnetic layer, the work function layer, and themetallic material to form a replacement gate; and forming a source/drainregion adjacent to the replacement gate.
 10. The method of claim 9,wherein a magnetic field applied on the gate dielectric by the magneticlayer is higher than about 0.1 Tesla.
 11. The method of claim 9, whereinthe magnetic layer is deposited using physical vapor deposition.
 12. Themethod of claim 9, wherein the depositing the magnetic layer comprisesdepositing a FePt layer or a NiFe layer.
 13. The method of claim 12,wherein the depositing the magnetic layer comprises depositing the FePtlayer, and each of platinum and iron in the FePt layer has an atomicpercentage between about 40 percent and about 60 percent.
 14. The methodof claim 9, wherein the depositing the magnetic layer is performed usingsputtering, and the method further comprises, after the sputtering,performing an annealing on the magnetic layer at a temperature higherthan about 1,000° C.
 15. A method comprising: depositing a gatedielectric comprising a portion over and contacting a semiconductorregion; depositing a magnetic layer over the gate dielectric, whereinthe magnetic layer comprises FePt; annealing the magnetic layer; afterthe annealing, depositing a diffusion barrier layer over the magneticlayer; depositing a metal-containing layer over the diffusion barrierlayer; and forming a source/drain region adjacent to the gatedielectric.
 16. The method of claim 15, wherein the annealing isperformed at a temperature higher than about 1,000° C.
 17. The method ofclaim 15, wherein the depositing the diffusion barrier layer comprisesdepositing a metal nitride layer.
 18. The method of claim 15, whereinthe diffusion barrier layer is in physical contact with the magneticlayer.
 19. The method of claim 15, wherein each of platinum and iron inthe magnetic layer has an atomic percentage between about 40 percent andabout 60 percent.
 20. The method of claim 15, wherein the magnetic layeris deposited at a temperature higher than about 500° C.